A toast to fine oak

by | Jul 31, 2018 | Winetech Technical, Practical in the cellar

The use of wood is an integral part of winemaking, but the implications of using this natural material extend beyond the cellar. By Bernard Mocke


The commercialisation of oak barrels started when the Roman armies and traders of old replaced clay amphorae with oak barrels which they favoured due to their weight and waterproof qualities.Today we know the science behind oak and oak alternatives is vast and complex. Winemakers are bombarded with a legion of choices: type of oak, which producer, length of ageing, oak alternatives and even if oak should be used at all during ageing and storage. Stainless steel tanks, amphorae (yes, they’re making a comeback) and food-grade polymer containers such as Flexcube are readily available options.


Quality comes at a price
The cost of barrels is a barrier for most producers, Chene SA national sales manager Clinton Le Seuer says. “We’ve seen a decrease in the number of barrels brought into South Africa every year, from the peak of 38 000 barrels in the mid-2000s to currently about 16 500.

High barrel prices have led to the increased use of oak alternatives and an influx of cheaper barrels. The cost has made winemakers pickier and they are purchasing fewer but better-quality barrels and using them only for their premium ranges.”

Lourensford cellar master Hannes Nel believes there’s no substitute for a well-made oak barrel to make top-quality wines. “At Lourensford we always aim for wine that has balance and harmony. The process starts in the vineyard and continues through to our barrel components and final blending of the wine.”

The oak is there to support and not overpower the delicate fruit flavours that winemakers work so hard to nurture in the vineyards and during the winemaking process. “We work with our barrel suppliers to get the best barrels for our style of wine. It’s a partnership. If we improve the quality of our wines we can grow the brand and buy more barrels.”

But not all barrels are created equally, Clinton says. “Winemakers should make sure their barrels come from a reputable supplier whose production and quality standards are reconcilable with their wine styles,” he says. “For instance, the effect of shorter stave seasoning times might not be noticed it at first, but they impart a harsh, sappy (astringent, mushroom, coconut, bitter, clove) character that you pick up on the palate as they leach into the wine.  And these barrels are worse on the second fill.”

But this is not the only potential quality threat. “Higher water content in barrels can lead to more pronounced vanilla characters,” Clinton says. “Then there’s the use of kilns to dry the oak during the stave-ageing process – it oxidises lignin and degrades cellulose and hemicellulose which leads to an increase in one-dimensional barrel profiles.”

The alternatives
The cost and versatility of oak alternatives are what make these products so highly sought after. They’re available as powders, chips, staves and even liquid tannins, and can be used to not only mature wines, but also for a variety of finings. Applications include softening or reducing bitterness, removing haze-forming proteins and colour stabilisation.

But these alternatives don’t suit everyone.  It’s a matter of desired wine style, so winemakers should do their homework before making a choice, Stellenbosch University oenology professor Wessel du Toit says. “I think it’s safe to assume the same quality wood that’s used for barrels is not used for alternatives due to the large cost differences involved. However, there are also excellent quality alternative oak products available. Winemakers should be more attentive to the composition of exogenous tannins and ask suppliers the tannin content/gram of the product for instance.”

It’s also safe to assume that the same maladies that haunt lesser-quality barrels also haunt inferior oak alternatives. But these products have several benefits if chosen carefully. “With oak alternatives you get to use more of the oak tree,” Clinton says. “There’s also the possibility of better and more affordable wines at low- and mid-spectrum price ranges. Other advantages include the masking of green flavours, colour binding, improved mouthfeel and better control of dosage.”

Appealing to the market

Wessel adopted a unique approach when he started working on a marketing plan for his wine range, Collatio. “One wine I made using oak as a selling point was a Perdeberg Shiraz. The grapes were destemmed, crushed and fermented in open bins. After pressing, the wine was divided between two old and new 300-litre French oak barrels and matured for about 18 months after which they were bottled separately.” Consumers thus have a great opportunity to experience first-hand the tremendous impact of oak on wine.

A usually lesser referenced but vitally important aspect of oak products is their sustainability. The green theme is on just about everyone’s lips these days and appeals are made to consumers that going green is not only the smart thing to do, but also the right thing to do. An admirable example of environmental stewardship is premium American oak barrel manufacturer Canton Cooperage which, in partnership with American Forests, planted one tree for every two barrels sold in 2015.

While there are pros and cons with all storage and maturation vessels, Hannes still favours wooden barrels.

“Some of the best wines I’ve tasted came straight from barrels, from Sauvignon Blanc on skins in foudre barrels in Italy where I worked to Chardonnay and Pinot Noir in Burgundy and Cabernet Sauvignon in Napa,” he says.

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